Power cranks

ABSTRACT

A variable length, pedal driven, crank mechanism, suitable for use on human powered vehicles; with gear driven transmission assemblies mounted on each end of an axle which is supported by and rotates on bearings. These arms have an inner and outer housing that bolt together forming rigid sealed assemblies, each containing a train of gears that engage the fixed, non rotating, pinion gears, transferring rotation to the proximal drive gears. The proximal gears have splined shafts that extend outside the primary housings on which secondary outer crank arms are attached. The outer crank arms are internally threaded on the side of their proximal ends for the attachment of pedals. This assembly causes the outer arms to extend on the down stroke and increases the amount of leverage available to the operator.

BACKGROUND OF THE INVENTION

The conventional set of cranks for a bicycle has a set length or distance from the center of the bottom bracket to the center of the pedal. Ground clearance restricts the length that the arms can be made. This also restricts the amount of leverage that the rider has to work with.

SUMMARY OF THE INVENTION

POWER CRANKS, however, allow the rider to have added leverage in the “sweet spot” or down stroke, while maintaining conventional levels of ground clearances. Figure One is a sectional view of a POWER CRANKS assembly. Item 1 being the section of bicycle frame in which the bottom bracket mounts. Item 8 is the axle, splined and threaded on each end for the left and right crank arm assemblies, Item 2. These arms are internally splined and mate closely to the axle, while being retained by the nuts, Item 12. Items 9 and 10 are pinion gears that thread into the frame; with bearings, Items 14, located inside to facilitate the rotation of the axle and crank arm assemblies around its axis. The crank arms are a housing, Items 2,3 and 4, which hold a train of spur gears, Items 28, mounted on pins, Items 22, and bearings, Items 23. These pins are sealed by static o rings, Items 26, and the bearings on which the spur gears rotate are retained by snap rings, Items 24. Item 5 is the outer crank arm on which the pedals are threaded. The outer crank arms are also splined internally and are clamped tightly to the external spline of the drive gears, Items 18, by the bolts, Items 21, while being retained by bolts, Items 20. The drive gears rotate on flanged ball bearings, Items 19, that are also sealed. The number of teeth on the drive gears and pinion gears are equal giving a ratio of 1:1. This maintains the attitude of the outer arm at assembly. If the outer arms and crank arm housings are mounted in such a way as to have them fully extended at the three o clock position; you have maximum leverage at this point. As the bicycle is pedaled the outer crank arm will remain parallel to the ground therefore maintaining necessary ground clearance and increasing potential leverage at the sweet spot or down stroke.

Figure Two is an enlarged view of the right side crank arm. In this view you can see the inner seal, Item 13, which helps hold contaminants out and oil in. Item 7 is the front chain ring. Item 15 is one of three bolts used to hold the ring to the crank arm. Items 16 are bolts used to hold the crank arm housing together. Item 17 is one of nine alignment sleeves in this view that also help make the housing more rigid. Item 6 is the pedal. Item 25 is a spacer-compression ring used to load the inner race of the bearing against the axle shoulder.

Figure Three is a side view of the right side crank arm housing showing the gears in mesh. The spline of gears, Items 9 and 18, are shown facing the viewer for clarity.

Figure Four is a side and sectional view of the inner crank arm housing showing the bolt and pin hole arrangement more clearly.

Figure Five is an enlarged view of the outer crank arm, its spline and clamp bolt.

Figures Six, Seven and Eight are side views of the left side crank arm housing its gear train, hole pattern and outer crank arm. The spline of gears, Items 10 and 18, are also shown facing the viewer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of the Power Cranks assembly. This is a sectional view with Item 1 being the frame member in which the assembly mounts.

FIG. 2 is larger sectional view of the right side crank assembly.

FIG. 3 is a view of the right side primary crank arm Item 2, with the Item 3 housing member removed. The splines as seen through the pinion gear Item 9 are part of the housing Item 2.

FIG. 4 is an inside view of the inner right side primary crank arm Item 3 with the sprocket Item 7. The sectional view is also Item 3 with sprocket.

FIG. 5 is a side view of the right side outer crank arm Item 5, with its' clamping bolt Item 21. The threaded hole at the top of the view is industry standard right-handed, for pedals.

FIG. 6 is a side view of the left side outer crank arm with its' bolt Item 21. The threaded hole at the top is industry standard left handed, for pedals.

FIG. 7 is a view of the left side primary crank arm Item 2, with the Item 4 housing member removed. The splines as seen through the pinion gear Item 10 are part of the housing Item 2.

FIG. 8 is an inside view of the inner left side housing member Item 4. 

1. A variable length crank mechanism suitable for use on human powered vehicles with these features: an axle mounted in sealed bearings with said axle being made hollow through the use of suitably strong tubing, for the reduction of weight, with external splines welded, or bonded to opposing ends, for the purpose of mounting gear driven transmission units to each of its' ends; the axle being threaded with right-handed threads on the right side and left-handed threads on the left side, for the application of threaded nuts for use in the retention of the primary crank arms, and to load the said primary crank arms, spacers, and bearing inner races against the axles shoulders; the axle and its' supporting bearings are mounted in pinion gears which are threaded for assemble to the frame member, these threads should be left-handed for the right side, and right-handed for the left side so that they remain tight with use, and do not rotate; with said pinion gears each having a precision groove machined around its' circumference for the containment of quad type o ring seals or equivalent, with the seals outside diameters making contact with and being compressed to industry standards for the retention of oil and exclusion of outside contaminants by the bores of the inner primary crank housings; with each tansmission unit having an outer arm with internal splines and bolts used to fasten it to the external splines of the proximal gear of the primary crank arm assemblies; with said proximal gears being positioned by and rotating on sealed, flanged bearings; with said outer crank arms being threaded to industry standards for the mounting of pedals; each primary crank arm contains a train of gears in their housing, even in number, between the fixed pinion gears and the proximal gears, to complement the preferred direction of rotation of the crank arm assemblies, that is downward pressure on the pedals attempts to rotate the outer crank arms in the same direction of the gears that engage the fixed pinion gears; with the number of teeth of the said fixed pinion gears being equal in number to the number of teeth on each of the proximal gears, producing a preferred ratio of 1:1, this maintains the attitude of the outer crank arm; with the outer crank arms mounted in such a way as to have them fully extended at the three o clock position, this gives maximum leverage at this point, as the vehicle is pedaled the outer crank arms remain parallel to the ground therefore maintaining the necessary ground clearance; with one of the primary crank assemblies having a chain sprocket or sprockets, depending on the application, mounted with bolts to the primary housing assembly; with the number of teeth on said sprocket also being dependent upon the application and desired ratio, with the chain being made to engage a suitable driven cluster of sprockets with a derailleur as used with multi speed bicycles, or it could also be made to engage a sprocket on a multi speed planetary transmission common to the bicycle industry; a gear train is enclosed within said primary housings, with each gear of the gear train between the pinion and proximal gears being mounted on bearings and pins which are sealed on each end with o rings that fit into grooves precisely machined into the face of each shoulder, with each shoulder also serving to keep the pin centered in its' housing; the said pins being hollow to reduce weight, with said bearings inner races precisely mating the major outside diameter of its' supporting pin, and being retained in the bore of the gears by snap rings and metal to metal fit; with spacers on each side of the inner race of said bearings, to keep them centered in their housing so that they do not rub the sides creating friction and reducing efficiency; with the inner and outer primary crank housings being bolted together with bolts and alignment sleeves, with these sleeves also serving as a strengthening member, preventing unwanted movement between the inner and outer housings; with the inner and outer housings mating surfaces being precisely machined and sealed with a suitable sealant for the retention of oil.
 2. A variable length crank mechanism consistent with claim 1 in which the number of teeth of the pinion and proximal gears in each primary housing is equal.
 3. A variable length crank mechanism consistent with claim 1 in which the number of idler gears that are engaged between the pinion and proximal gears are even in number.
 4. A variable length crank mechanism consistent with claim 1 in which the primary housing is sealed for the containment of a lubricant.
 5. A variable length crank mechanism consistent with claim 4 in which the pinion gears have a precision groove cut around their circumference for the containment of a seal suitable for the exclusion of contaminants and the containment of lubricant.
 6. A variable length crank mechanism consistent with claim 5 in which the inner housing of the primary crank arms have a precision bore concentric to the rotation of the axle that is used as a seal fit.
 7. A variable length crank mechanism consistent with claim 4 in which the pins that support the idler gears are sealed on each end to the primary housings with o rings.
 8. A variable length crank mechanism consistent with claim 4 in which the bearings that support the proximal gears are sealed on their outer side.
 9. A variable length crank mechanism consistent with claim 1 in which the primary housings are bolted together and use precise fitting alignment sleeves to increase the rigidity of their assembly.
 10. A variable length crank mechanism consistent with claim 9 in which the bearings that support the proximal gears on each end are flanged, with each flange fit to counter bores in the inner and outer housings of the primary crank arm.
 11. A variable length crank mechanism consistent with claim 9 in which the proximal gears have shoulders for the flanged bearings to be seated against; with one end of each proximal gear having splines and internal threads, on the same end, for the fixation and containment of the outer crank arm.
 12. A variable length crank mechanism consistent with claim 11 in which the outer crank arms have internal splines that precisely fit the external splines of the proximal gears, with the splines being split parallel to their axis, with a through bolt perpendicular to this split to tighten the assembly.
 13. A variable length crank mechanism consistent with claim 12 in which the outer crank arms have a shoulder on their inner side that circumvent the splines and are pulled tightly against the flanged bearings inner race with bolts to compliment the assembly, and its' rigidity.
 14. A variable length crank mechanism consistent with claim 1 in which the outer housings of the primary crank arms are internal splined and shouldered to precisely fit the external splines of the axel.
 15. A variable length crank mechanism consistent with claim 1 that has the outer crank arms threaded to industry standards for the acceptance of bicycle pedals.
 16. A variable length crank mechanism as an assembly consistent with claims 1 through 15 that allows for an increase in leverage through the use of pinion gears and proximal gears with an equal number of teeth, obtaining a final ratio of 1:1; with said gears having an even number of idler gears in mesh with them; allowing for the aforementioned complementary direction of rotation and extension of the outer crank arm, with pedals, in relation to the axis of the axel. 